As everyone knows, LED illumination has irreplaceable advantages, such as energy saving, low power consumption, and electrical-to-optical conversion efficiency near to 100%. It can save no less than 80% energy and has a longer service lifetime compared with the traditional light source with the same illuminating efficiency. In view of the above advantages, the LED is used more and more as a light source such as a lot of LED retrofit lamps available in the market. Such LED retrofit lamps have the same appearance and profile as the traditional light source such as incandescent lamp, thus they can be more applicable to the existing illuminating systems as a light source. LED has been widely used in current illuminating device.
With the technology development, LED package itself can reach high efficiency, such as 140 lm/W for cold white and 90 lm/W for warm white and they are supposed to have a long lifetime as to 50,000 hours, but when the LED is integrated into a retrofit lamp together with an LED driver, a thermal management device and an optical component, the efficiency and the service lifetime of the retrofit lamp are highly dependent upon how to design the driver, the heat sink device and the optical component. Some of the electrical power consumed in the LED is converted to heat rather than light. According to statistics of U.S. Department of Energy, 75% to 85% of energy used to drive the LED is converted to heat, and the heat must be conducted from the LED die to the underlying PCB and heat sink device. If the heat cannot be conducted timely, the light output performance of the LED will be reduced and a color shift will be produced in a short term, and the service lifetime of the LED will be shortened in a long term.
Various heat sinks have been designed in order to improve the heat dissipating capability of the illuminating device. However, for the sake of industrial protection, the LED is usually arranged in a housing of the illuminating device or in an enclosed space of the heat sink, but the space between the lens and the circuit board bearing the LED is small, and effective air convection cannot be carried out in this space, thus, heat exchange between the LED as heat source and the outside is hindered, which reduces the heat dissipating performance of the illuminating device to a great extent, and further reducing the efficiency and the service lifetime of the illuminating device.